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Constructed wetlands (CWs) are a group of novel, natural wastewater treatment technologies which principally house microbes with help of plants and filter media. The denitrification rates in vertical flow constructed wetland (VFCW) are sensitive and in most cases complete nitrogen removal does not occur. In current study, two systems were evaluated, 1st was partial saturated up-flow VFCW and the 2nd was hybrid pilot scale setup of VFCW and floating treatment wetland (FTW) in series. Both these systems were implemented at single household scale for treatment of greywater. VFCW filter media were river sand and gravels with Canna indica as macrophyte. FTW rafts were made of thermocol sheets covering 100% of water surface in tank. System sampling was done for every 3rd day and pollutant removal performance was measured in terms of COD, total nitrogen (TN), ammoniacal nitrogen (NH4-N), nitrate (NO3-N), nitrite (NO2-N), and o-phosphate (PO4-P) concentrations of influent and effluent. Saturated VFCW system removed 89.09%, 78.7%, 67%, 68.74%, 94.6%, and 86.01% whereas hybrid wetland removed 91.5%, 92.32%, 82.2%, 71.13%, 97.25%, and 89.37% of COD, TN, NH4-N, NO3-N, NO2-N and PO4-P respectively. After stable pollutant removal trend, FTW macrophyte roots were harvested and subjected to metagenomic analysis on Illumina platform to identify microbial diversity and functional annotation related to nitrogen and phosphate removal. Microbial diversity showed Pseudomonas, Bacteroides, Clostridium, Azoarcus, Achromobacter as dominant top 5 genus. This group of genus highlights denitrifying microbial abundance greater than VFCW metagenomes microbial population. The presence of significantly higher denitrifying microbes in FTW confirms higher denitrification rate than VFCW, resulting in overall more Nitrogen removal by the system.

Laundry processes are huge water consumers and contribute to wastewaters in high volume. In the current report, treatment of greywater (GW) was studied from commercial laundry in BITS Pilani, KK Birla Goa Campus, India, which produces around 2–2.5 m3/day of GW. Source laundry GW showed physicochemical parameters like chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammoniacal N (NH4–N), nitrate (NO3–N), nitrite (NO2–N), orthophosphate (PO4–P) and pH in the range of 600–650 mg/L, 350–370 mg/L, 9–12 mg/L, 15–21 mg/L, 14–22 mg/L, 28–35 mg/L and 7.48–8.10, respectively. The treatment system included French‐type two‐stage vertical flow constructed wetland (VFCW) preceded by anaerobic filter tank filled with 3D plastic support. Wetland beds were made up of sand and gravel as filter media, and Canna indica was used as macrophyte. Pretreatment by anaerobic filter resulted in the increase in residence time of GW and reduction of pollutant load to wetland beds, thus preventing clogging of Stage 1 wetland. Sampling and water quality data analysis was performed weekly for 26 weeks. Outlet pollutant levels showed 96.35% removal of organic matter, 79.93% removal of nitrogen and 95.04% removal of orthophosphates. The pH of outlet water was 7.35, which is well below discharge permissible limits. Treated water quality was below Central Pollution Control Board (CPCB), India, permissible limits for discharge, and the cost of treating GW by the system is 1.11 USD/m3 which is very feasible in country like India. Treated water is suitable for nonpotable options like gardening of central lawns in BITS Pilani Goa, floor cleaning of laundry and construction purpose.